The present invention seeks to improve communication across a network which includes mobile wireless network nodes, for example a mesh network. Such mobile wireless network nodes may be deployed as part of an ad hoc network required at short notice, for example, when emergency services attend an incident at which telecommunication facilities are required to be provided quickly on-site. (Such a mobile ad hoc network may sometimes be referred to as a MANET.) Hard-wired, mobile phone, 3G, 4G, and satellite communications systems are not always readily available or convenient to use and as such radio-based mobile wireless network access points may need to be rapidly deployed to provide an effective communications system on the ground. In certain circumstances, there may be movement of the network access points/nodes in the network. The ability to transmit data from one node to another may change rapidly according to local environmental conditions.
Communication networks of the prior art cater for giving priority to certain types of communication and routing protocols exist which give priority to certain traffic, typically based on quality of service (“QoS”) requirement information within the data packet headers. Software applications can set minimum QoS parameters for the transmission of data, which may then be acted on by routers to prioritise traffic appropriately. The differentiated services (DiffServ) architecture provides a mechanism for applications to achieve certain levels of service, by means of routers differentiating between different types of data traffic. Details of the DiffServ architecture and protocols are set out in RFC 2474 (“Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers”) and RFC 2475 (“An Architecture for Differentiated Services”)—available from the Internet Engineering Task Force's (IETF) Network Working Group's RFC (“Request for Comments”) set of documentation. The integrated services architecture (“IntServ”—see IETF's RFC 1633) also provides a means of guaranteeing QoS, by requiring each router on the route between source and destination to reserve sufficient bandwidth to ensure the QoS requirements are met (i.e. operating in a virtual circuit-switching mode). Both DiffServ and IntServ architectures have short-comings when operating in a MANET, because congestion and/or rapid changes in bandwidth, link quality etc. can readily occur at short-notice. When an application on a source computer attempts to send data to a destination computer via a MANET, the application can set QoS criteria, but if the network is unable to meet the minimum criteria the data may never reach its destination or be received incompletely or in a corrupted state. The destination computer may when receiving incomplete or corrupted data be able to communicate such facts to the source computer, and the destination computer may, for example by means of manual intervention, request that the data be resent. In such a case, the network connection may have deteriorated yet further making retransmission of the data more problematic. Also, retransmitting data can in itself cause unnecessary congestion of the network, because data is transmitted more than once across at least part of the same network. If the receipt of the data is time-critical or time-sensitive, the failure to send the data from source to destination may be viewed as a failure that it is not subsequently possible to remedy. Such problems are particularly acute when seeking to transmit data across a rapidly changing MANET.
US 2012/0002615 describes a means of communication across a MANET in which types of service are differentiated and a decision engine permits or prevents communication of certain types across the network, according to how demanding/important (how critical) the communication types are. Such a regime provides a very coarse means of provisioning network resources to traffic, and could readily prevent traffic other than that of the utmost critical importance dominating the network.
US 2011/0110309 discloses network node devices which cooperatively route traffic flow amongst wired and wireless networks by employing multi-path management processes. The possibility of a network device, programmed with a multi-path management software product, determining a particular path partly in dependence on the type of data is disclosed.
WO 2010/028311, relating to “enhanced wireless ad hoc communication techniques”, discloses the concept of generating a cost-based routing matrix for a network node which results in a routing table which takes account of traffic type, for example by means of weighting according to traffic type.
The patent publications mentioned above provide suggestions for sophisticated routing of traffic across networks including wireless nodes, including taking account of the type of data being transmitted, but would appear to represent overly complicated solutions that might be difficult to implement efficiently in practice, especially in the context of routing data efficiently in a fast changing wireless ad hoc network, where the conditions of the network may change so rapidly as to render such sophisticated systems of little practical use, particular if and when the network is congested and/or required to serve volumes of traffic far beyond its current capacity.
The present invention seeks to mitigate one or more of the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved method of routing traffic within a data network.